Provide an easy way to generate DeepCopy function for data class. DeepCopy only takes effect on the component members i.e. the members declared in the primary constructor.

Use Kotlin Reflection to provide an extension function for Any so that any data class can simple call deepCopy() to copy itsself.

See the test code below:

data class Speaker(val name: String, val age: Int)

data class Talk(val name: String, val speaker: Speaker)

class DeepCopyTest {
    @Test
    fun test() {
        val talk = Talk("DataClass in Action", Speaker("Benny Huo", 30))
        val newTalk = talk.deepCopy()
        assert(talk == newTalk)
        assert(talk !== newTalk)
    }
}

talk equals newTalk since the values of their members are equal while they do not ref to the same object.

This library has been deloyed to jcenter.

compile 'com.bennyhuo.kotlin:deepcopy-reflect:1.1.0'

If you concern about the runtime efficiency, apt may be the solution. You can simply annotate the data class you want to deep copy with a DeepCopy annotation:

@DeepCopy
data class Speaker(val name: String, val age: Int)
@DeepCopy
data class Talk(val name: String, val speaker: Speaker)

Extension function deepCopy will be generated according to the components:

fun Talk.deepCopy(name: String = this.name, speaker: Speaker = this.speaker): Talk = Talk(name, speaker.deepCopy())

fun Speaker.deepCopy(
    name: String = this.name,
    age: Int = this.age,
    company: Company = this.company
): Speaker = Speaker(name, age, company.deepCopy()) 

Notice that deepCopy is called recursively if the member type is also a data class annotated with a DeepCopy annotation. Hence, if you remove the annotation for Speaker, generated function would be like:

fun Talk.deepCopy(name: String = this.name, speaker: Speaker = this.speaker): Talk = Talk(name, speaker)

//And no deepCopy for Speaker.

This library has been deloyed to jcenter, but the compiler depends on the experimental artifact kotlinx-metadata-jvm so you should also add a maven repo https://kotlin.bintray.com/kotlinx/ to compile.

repositories {
    jcenter()
    maven { url "https://kotlin.bintray.com/kotlinx/" }
}

...
apply plugin: "kotlin-kapt"
...

dependencies {
    kapt 'com.bennyhuo.kotlin:deepcopy-compiler:1.3.0-rc1'
    compile 'com.bennyhuo.kotlin:deepcopy-runtime:1.3.0-rc1'
}

• [Feature] Collections/Maps are supported.
• [Feature] Prebuilt types are supported by annotation DeepCopyConfig. See Prebuilt
• [Bug] Fixed: Data classes with their dependencies should be place into the same package.
• [Bug] Fixed: Improperly import a type variable when component type is not reified.

• [Feature] Add support for nullable types. It will allow copy loop sematically and an exception will be thrown to respond when compiling. See Recursive.kt.

• [Feature] Add default values to generated deepCopy functions.

MIT License

Copyright (c) 2018 Bennyhuo

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